Biological Opinions - Bureau of Reclamation

12.4.1.2 Response
12.4.1.2.1 Adults
Minimum daily average flows under the proposed action are at least 950 cfs during the period of
upstream migration. Reclamation (2012) determined that the proposed action is unlikely to have
an appreciable impact on the mainstem migration of adult coho salmon from low flow blockage.
Reclamation made their determination by comparing the number of days the proposed action will
result in IGD flows below 1,000 cfs in the fall to those observed in the POR. Flows less than
1,000 cfs may hinder adult salmon migration into the tributaries (Reclamation 2012). Even
though the proposed action will result in more days in the fall than the observed POR when
flows are less than 1000 cfs, Reclamation determined that the hydrologic conditions under the
proposed action will likely support adequate adult passage.
While NMFS does not agree with Reclamation’s use of the observed POR as a metric to
represent adequate migration, NMFS concurs with Reclamation’s determination that the
proposed action is not likely to adversely affect adult coho salmon migration in the mainstem
Klamath River. Coho salmon escapement monitoring have confirmed successful adult passage
in the mainstem Klamath River when IGD releases were at least 950 cfs in the fall (e.g., FWS
mainstem redd/carcass surveys, CDFW Shasta and Bogus Creek video weir studies, IGH
returns). The apparent lack of coho salmon migration delays resulting from past IGD flows of at
least 950 cfs is consistent with studies reviewed by Jonsson (1991) that suggest low flows are
less likely to delay adult fish migration in large rivers, such as the mainstem Klamath River. In
addition, water temperature in the mainstem Klamath River are cool or cold in the late fall and
winter, and is not expected to impede coho salmon adult migration. In addition, flow variability
incorporated into the proposed action will likely provide an environmental cue to stimulate adult
coho salmon upstream migration when flows in the mainstem Klamath River mimics natural fall
and winter freshets.
12.4.1.2.2 Eggs
As discussed in the Effects to SONCC Coho Salmon ESU Critical Habitat section and assuming
coho salmon spawning habitat is similar to Chinook salmon, NMFS expects that the proposed
action will provide suitable quantity of coho salmon spawning habitat for successful spawning
and egg incubation. While the proposed action will likely reduce the duration, magnitude and
frequency of fine sediment mobilization from spawning gravel when IGD flows are below
10,000 cfs, adult coho salmon are able to clean fine sediment from spawning gravel (Kondolf et
al. 1993, Kondolf 2012) prior to depositing eggs. Therefore, eggs in the mainstem Klamath
River are not likely to be adversely affected by the proposed action.
Also, while the proposed action will likely reduce mainstem flows from October to December in
less than average water years (> 45 percent exceedance; Table 11.8), coho salmon eggs in the
mainstem are not expected to be dewatered because the average flow reductions are limited to
approximately 70 to 140 cfs, which amounts to a stage height reduction at IGD of up to
approximately 2.4 inches. The proposed action’s ability to simulate flow variability at IGD and
the naturally increasing flows during the winter from storm events downstream of IGD will
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